rcd not tripping

[matt12321]

looking for a fault on a caravan where the rcd trips when a main earth is added. with no main earth the rcd want trip. the caravan has only got an earth path via bonding from the earth rod to the db and no main earth from the earth rod to the db.

zs is 66.4 on sockets 67 on lights and 66 on the shower.

the board has been tested and no faults found. as soon as u add 4mm or a 10mm main earth the rcd trips when say the cooker or shower are turned on.

 

[topquark]

That's from the RCD testing then, not a ramp test. The ramp test should give one figure only.

To prove it leave the cooker circuit isolated when turning on the CU, with the "main earth" connected.

 

[Had8Lives]

Sounds like you have a fault on an appliance. You say it trips with an Earth rod connected when you turn on an appliance.

 

[matt12321]

tried with the cooker unplugged and still no luck, still trips out.

so im lost now

 

[topquark]

Don't unplug the cooker, isolate the circuit completely. If you're sure all the wiring is ok then start with all circuits off and engage them one at a time until the RCD trips at least you'll know what circuit is causing the issue (assuming it's just one). Once you have identified a suspect circuit isolate them all again and just engage the suspect circuit (which should trip the RCD). Then you need to just find what on that circuit is causing the issue(s).

 

[matt12321]

sweet. dint think about going at it that way.

thanks for your help

 

[Des 56]

Trying to think of something to help you,but its difficult as you know, trying to remote fault find

Here is a procedure I would do, that may have benefit

If all tests reveal nothing untoward,then connect up the earth conductor to an empty board (dis connect the lot)
Re test the Rcd,a ramp test would give the confirmation that its tripping with a suitable leakage current,but as you have changed the Rcd,a faulty trip problem may be dis carded

Check the continuity of the circuit cpcs and their continuity to the caravan frame and earth bar
check also the supply voltage between l-n l-e n-e

Connect and operate the cooker until there is plenty of heat in the elements,maybe one is breaking down
Leave any lights dis connected,maybe an un noticed neutral earth fault on the lights that does not have sufficient leakage to trip by itself,but may cause the tripping when a large load is applied

Connect up the shower and operate,insulation testing the dist board as you progress
Finally any lights

Something gottta give
Good luck and when you identify the the problem,as I'm sure you will, let us know what it was

 

[matt12321]

thanks for that des.

yeh definitely, im sure it will help many who have reading the thread and getting involved

thanks again

 

[topquark]

Trying to think of something to help you,but its difficult as you know, trying to remote fault find

Here is a procedure I would do, that may have benefit

If all tests reveal nothing untoward,then connect up the earth conductor to an empty board (dis connect the lot)
Re test the Rcd,a ramp test would give the confirmation that its tripping with a suitable leakage current,but as you have changed the Rcd,a faulty trip problem may be dis carded

Check the continuity of the circuit cpcs and their continuity to the caravan frame and earth bar
check also the supply voltage between l-n l-e n-e

Connect and operate the cooker until there is plenty of heat in the elements,maybe one is breaking down
Leave any lights dis connected,maybe an un noticed neutral earth fault on the lights that does not have sufficient leakage to trip by itself,but may cause the tripping when a large load is applied

Connect up the shower and operate,insulation testing the dist board as you progress
Finally any lights

Something gottta give
Good luck and when you identify the the problem,as I'm sure you will, let us know what it was

A good point Des, had that with a small worktop cooker causing nuisance tripping, the cooker tested fine standalone when cold, right little bugger to find that was . Turned out to be the top elements in the cooker starting to break down.

 

[london_uk]

RCD before the meter ?

 

[topquark]

RCD before the meter ?

Yep, it's a caravan site. You get all sorts of weird crap with them.

 

[topquark]

Largely historic as a lot of sites were run with no separate metering for each van when done initially.

 

[Des 56]

Yep, it's a caravan site. You get all sorts of weird crap with them.

Are you still talking Rcds or occupants

 

[matt12321]

yeh and this site is no exception. definitely historic topquark

 

[topquark]

More usual arrangement these days is incoming supply to meter. Double Pole Isolator with BS88 (63A), SWA to CU with normal(ish) arrangements from there. Usually SWA is 3 core (with grey used for earth). Earth connected into MET in enclosure (either inside the van or outside). Frame of van bonded to MET (or occasionally earth bar in CU). Sometimes additional earth rod (as necessary).

There are, of course, many variations on a theme with this, still it keeps things entertaining.

 

[gamblor6]

sounds like an ir fault to me. had this recently, call out, sat night, any time we turn anything on power trips, ok ill be there soon, sure enough as stated.
said to them ok this just doesnt happen, any work done here? ie pictures put up etc, oh aye was the answer, the db was just fitted today, guy had probs with it tripping but said it was fine now, no real testing had been carried out, stripped accessible live and neutral at a light, 3 kids runnin everywhere, one of wich emptied the contents of there stumoch on the floor as i scratched my head here. turns out the neutrals were not right at the db plus one light the screw fixing to the ceiling JUST niked the neutral. nightmare believe me. midnight i got home that night lol.